Cartridge

Circuit Diagram

Background

The game cartridge uses an 8KB FRAM chip for storage. The chip is communicated with over SPI rather than being connected directly to the bus. The tradeoff with using an SPI memory module is that there is a time delay for loading the game, but the design is simple. To use SPI with a 65C22, 4 pins are needed. The 65C22 has no hardware support specifically for SPI, so the protocol must be bit-banged.

Pin

Description

PB0

Clock - Using this pin means, INC and DEC can be used to oscillate the clock signal easily